Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
Impaired Long-Lived Assets Held and Used [Line Items]
Allowance for doubtful accounts	$ 11.1	$ 12.0
Rerate reserve as a reduction to accounts receivable	12.5	8.8
Deferred revenue	25.7	28.1
Foreign currency transactions gains (losses)	$ 2.7	$ (4.0)	$ 0.9
Risk-free rate for maturities of workers' compensation claims	2.60%	1.50%	1.01%
Risk-free rate for property damage and liability claims	2.50%	1.30%	0.80%
Accrued claims and insurance	$ 350.3	$ 360.7
Amortization of prior net losses	14.6	12.9	$ 13.7
Amortization of prior net service credit	(0.4)	0.0	0.0
Reclassification of foreign currency translation gains to net income	0.0	0.0	10.4
Net cash provided (used) in financing activities	(33.9)	(96.2)	(73.2)
Nonoperating Income (Expense)	(111.6)	(137.1)	(119.9)
Labor and Related Expense	$ 2,950.0	2,884.2	2,802.9
Labor Force Concentration Risk [Member] | Workforce Subject to Collective Bargaining Arrangements [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Percentage of labor force	78.00%
Accounting Standards Update 2016-09
Impaired Long-Lived Assets Held and Used [Line Items]
Net cash provided (used) in financing activities		(2.4)	(0.7)
Accounting Standards Update 2017-07
Impaired Long-Lived Assets Held and Used [Line Items]
Nonoperating Income (Expense)		(20.6)	(20.2)
Labor and Related Expense		$ (20.6)	$ (20.2)
Subsequent Event | Accounting Standards Update 2016-02
Impaired Long-Lived Assets Held and Used [Line Items]
Operating lease, right-of-use asset				$ 375.0
Operating lease, liability				$ 375.0